Soybean milk, soybean milk pack and process for producing the same and process for manufacturing tofu by using the same

ABSTRACT

A process for producing a soybean milk and soybean milk pack includes cooking ground soybeans with the use of superheated steam containing no or little oxygen, thus extracting soybean proteins to give a cooked bean juice of the soybeans; separating a solid soybean curd lees in the oxygen-free state without cooling the bean juice to give a soybean milk containing no or little dissolved oxygen and having soybean proteins suspended therein. The process also includes filling the thus produced soybean milk into pack containers in an oxygen-free environment with no or little dissolved oxygen without heating or cooling the soybean milk, sealing the containers, and then storing at 1 to 10° C. A process for manufacturing a soybean curd includes introducing the above soybean milk or the contents of the soybean milk packs into an insulating container for manufacturing soybean curd, adding an appropriate amount of coagulant thereto followed by mixing, immersing non-corrosive electrodes in the insulating container, passing an alternating current between these electrodes under such conditions that no electrolysis occurs, and heating the mixture to give a soybean curd.

TECHNICAL FIELD

The present invention relates to soybean milk and soybean milk packwhich can be stored for a long time without the deterioration offreshness of the soybean milk, and relates to methods for manufacturingthe soybean milk and the soybean milk packs, and relates to a method ofmanufacturing a delicious and mild soybean curd (a tofu in Japanese)which can be easily and stably manufactured anywhere even bynonprofessionals without failure, using the thus manufactured soybeanmilk and the soybean milk packs and can be eaten in a fresh and hotstate just after it is manufactured.

BACKGROUND ART

A soybean curd, being nutritious and manufactured by coagulating soybeanprotein is a food which has been eaten by many people. Thus, the soybeancurd is manufactured by speciality manufacturers in large amounts andsold in supermarkets and the like in large quantities at less expensiveprice. However, the packed soybean curd sold in large quantities iseaten after a time passes from the time it was manufactured, the taste,deliciousness, smell, and feeling in the mouth, such as on the teeth ortongue thereof are inferior to those of a fresh soybean curdmanufactured by soybean curd stores in town. Consequently, since asmall, traditional soybean curd stores in town supply a fresh andtasteful soybean curd to dining tables of homes, there exists a soybeancurd which is manufactured by hand using a conventional method, althoughthe quantity thereof is small.

Incidentally, a soybean curd is manufactured by grinding soybeansimmersed in water; boiling the thus obtained ground soybeans; obtaininga “go” (bean juice which is obtained by grinding soybeans immersed inwater or thereafter by boiling ground soybeans) by extracting soybeanprotein from the boiled soybeans; obtaining soybean milk by separatingan okara (solid soybean curd lees) as a solid matter from the bean juice(or nigo which is boiled bean juice); cooling the thus obtained soybeanmilk; mixing the cooled soybean milk with a coagulant such as a “nigari”(magnesium chloride which is usually used as an aqueous solution) tothereby obtain a mixture of the soybean milk and the nigari; andcoagulating the soybean protein by heating the mixture. Calcium sulfateand the like are used as the coagulant of the soybean milk, in additionto the nigari.

As described above, the soybean curd is a very popular food. However, tomake a soybean curd having a good taste and a good smell, not only highspeciality is required in a technique for manufacturing soybean milk ofhigh quality as a raw material of the soybean curd and in a techniquefor adding a nigari to the soybean milk and coagulating the soybean milkbut also the entire soybean curd manufacturing steps from a step ofboiling ground soybeans to a step of coagulating the soybean milk mustbe successively carried out. As a result, a small soybean curd store iscompelled to work from an early morning without a rest to supply a freshand tasteful soybean curd so that it is in time for family breakfast.

To produce the soybean milk as the raw material of the soybean curd,ground soybeans are conventionally boiled in a dedicatedbean-juice-manufacturing caldron. The bean-juice-manufacturing caldronused to the manufacture of soybean milk, a soybean curd andmembrane-like soybean curds (“yuba”) comprises a cylindrical caldronmain body having closed upper and lower ends, a charge port disposed atlower portion of the caldron main body for charging a raw material ofbean juice such as ground soybeans to which water is added or the heatedones thereof, a discharge port disposed at upper portion of the caldronmain body for discharging the raw material after it is processed in thecaldron, and a steam injection pipe having a plurality of injectionports simply formed therethrough and installed in interior of thecaldron main body.

Steam used in the conventional bean-juice-manufacturing caldron isair-containing steam obtained by simply heating ordinary water. Theordinary water contains oxygen in an amount of 8-10 ppm.

In the conventional bean-juice-manufacturing caldron, the steam injectedfrom the injection ports of the steam injection pipe is injected in aradial direction. The steam injected in the radial direction collidesagainst the inner peripheral wall of the caldron main body and losetheir motion energy so that the flow rate of the streams is reduced.Therefore, the steam having the reduced flow rate cannot sufficientlyturn and flow into the space located backward of the injection ports inthe caldron main body and the steam only moves upward in the caldronmain body. As a result, the steam is in good contact with the rawmaterial of bean juice or the heated one thereof (hereinafter, they arereferred to as raw material of bean juice as a whole) which is locatedin the vicinity of the radially injecting passages of the steam which isdirected radially from the injection ports so that the raw material ofbean juice located at the position is sufficiently heated with the heatof the steam. However, since the steam comes into contact with the rawmaterial of bean juice in a small quantity which is located in the spacebackward of the injection ports of the caldron main body, the heat ofthe steam is not sufficiently transmitted to the raw material of beanjuice located at the backward position. Thus, the raw material of beanjuice cannot be heated with a necessary quantity of heat. As a result, apart of the raw material of bean juice is sufficiently heated and theother part thereof is insufficiently heated, whereby the raw material ofbean juice is unevenly boiled. There is caused thereby a problem thatsoybean milk of good quality cannot be obtained from the unevenly boiledbean juice.

In the conventional bean-juice-manufacturing caldron, since steam cannotbe uniformly and sufficiently supplied to the raw material of beanjuice, the steam cannot sufficiently transmit their heat to the rawmaterial of bean juice. Accordingly, a large quantity of the steam stayin the upper portion of the caldron main body while holding a sufficientquantity of heat at high temperature and increase the pressure of theupper portion of the caldron main body as a residual steam. Thus, therearises a problem that the raw material of bean juice is pushed out intothe discharge port of the caldron main body in a quantity larger thannecessary, the feed of the raw material of bean juice in the caldronmain body cannot be properly controlled, the raw material of bean juicehas a portion to which the heat of the stream is transmitted well andwhich is sufficiently heated and a portion which is insufficientlyheated, whereby the raw material of bean juice is unevenly boiled, beanjuice of good quality cannot be produced and thus a soybean curd of goodquality cannot be manufactured.

Incidentally, when a soybean curd is manufactured by coagulating soybeanmilk by adding a nigari (magnesium chloride) as a coagulant thereto, thenigari can well extract sweetness and flavor of soybeans. However, sincethe coagulating reaction proceeds too promptly, this process cannot beoften performed successfully. Thus, not only a sophisticated techniqueis required to mix the nigari with the soybean milk but also a speed atwhich the nigari performs a coagulating reaction must be controlled byminutely monitoring a coagulation state thereof and controlling thetemperature thereof. Therefore, conventionally, soybean milk is cooledso as to be slowly coagulated, and after a nigari is well mixed with thesoybean milk, the thus obtained mixed solution is slowly heated withsteam or in a water bath. Thus, there is a problem that 1-2 hours arenecessary to the heating of the mixed solution, which is veryinefficient. Further, since a long time is necessary to the heating ofthe mixed solution, the outside portion of a soybean curd is exposed toa very high temperature as compared with the inside portion thereof andheat is excessively applied to the outside portion of the soybean curd,from which a problem arises in that the outside portion of the soybeancurd is heated secondarily and tertiarily and the water keeping propertyof the thus obtained soybean curd becomes poor.

As described above, when soybean milk, which is obtained by separatingan okara from an insufficiently heated bean juice (of low quality), isused in the mixture of the soybean milk with a coagulant such as anigari and the like which requires the sophisticated technique, it isstill more difficult to make a soybean curd of high quality because thesoybean milk is also unevenly manufactured. This is because that soybeanmilk obtained from a uniformly and sufficiently heated bean juice (ofhigh quality) not only promptly reacts to a coagulant but also is mixedtherewith quickly as compared with the unevenly manufactured soybeanmilk. That is, when a coagulant such as a nigari or the like is added tosoybean milk manufactured from an unevenly cooked bean juice in themanufacture of a soybean curd, the coagulant is concentrated at theportion of the soybean milk which was obtained from the sufficientlyheated portion of the bean juice before a coagulanting reaction occursto the entire soybean milk, the soybean milk is reacted to the coagulantpromptly, and thus the coagulant cannot be uniformly mixed with theentire soybean milk. As a result, there is a problem that a soybean curdof high quality having elasticity and a sufficient water keepingproperty cannot be still more manufactured.

Incidentally, since steam is obtained by simply heating ordinary waterin the conventional bean-juice-manufacturing caldron, it cannot beavoided for air to be mixed with the steam when it is manufactured sothat oxygen is contained in the steam. When a raw material of bean juiceis boiled with the steam in which the oxygen is mixed, it is also mixedwith or dissolved in soybean milk obtained by separating an okara frombean juice. Thus, there is a problem that the soybean milk isdeteriorated in a very short period of time and a soybean curd of highquality cannot be manufactured from the soybean milk as well as a lot ofporosities are formed in the soybean curd due to the dissolved oxygenand the taste thereof becomes deterigated. To cope with this problem, afresh soybean milk must be used at once for the manufacture of a soybeancurd. Thus, a soybean curd of high quality is manufactured only by aspeciality manufacturers and it is impossible to supply a fresh soybeancurd to homes and eating houses.

Further, soybean milk is an excellent drink which does not cause atopicdermatitis and allergy symptoms different from a cow's milk regardlessof that it is as nutritious as the cow's milk and less expensive.However, a fresh soybean milk manufactured from the conventionalbean-juice-manufacturing caldron cannot be stored for a long time unlessit is sterilized at high temperature. However, when the soybean milk issterilized at high temperature, it is somewhat denatured and thedeliciousness characteristic to the soybean milk is lost. Consequently,there is also a problem that a fresh soybean milk having deliciousnessand a good taste is sold only in the vicinity of a small-scaledspeciality soybean curd manufacturers in a very small quantity andcannot be freely distributed in a market.

A leading subject of the present invention is to solve the aboveproblems of the conventional techniques and to provide soybean milk ofhigh quality, soybean packs into which the soybean milk of high qualityis filled, soybean milk manufacturing method capable of manufacturingthe soybean milk of high quality and soybean milk pack manufacturingmethod of manufacturing the soybean milk packs.

The soybean milk of high quality can be obtained by separating a solidmatter from a uniformly boiled bean juice of high quality obtained byusing a novel caldron. The soybean milk can be stored without the needof high temperature sterilization while keeping the sweet taste, smell,deliciousness and freshness characteristic to the soybean milk; is lessdeteriorated even if it is stored; and can be drunk as a drink as it is,in addition to that it is used as a raw material of a soybean curd ofhigh quality. The soybean milk packs can be stored for a long time; canbe handled easily; and can be supplied to an ordinary home and an eatinghouse as well as to a speciality soybean curd manufacture.

Another subject of the present invention is to provide a soybean curdmanufacturing method capable of supplying a just cooked and freshsoybean curd of high quality which can be manufactured easily in a shorttime by a nonprofessional in ordinary homes and eating houses, inaddition to speciality soybean curd manufacturers, using the soybeanmilk of high quality and the soybean milk packs. The soybean curd madeby the method is of high quality, namely, fresh, tasteful, delicious andmild felt on the tongue and has a good water keeping property withoutporosities formed therein.

DISCLOSURE OF THE INVENTION

To solve the above problems, a first aspect of the present inventionprovides soybean milk which is characterized by containing soybeanprotein suspended therein and oxygen dissolved therein in an amount of 5ppm or less without heat treatment.

It is preferable that the soybean milk contains substantially no oxygendissolved therein.

A second aspect of the present invention provides a soybean milk packwhich is characterized by comprising soybean milk containing soybeanprotein suspended therein and oxygen dissolved therein in an amount of 5ppm or less without heat treatment and a pack container into which thesoybean milk is filled, and which is stored at a temperature of 1°C.-10° C.

It is preferable that the soybean milk pack contains substantially nooxygen dissolved in the soybean milk and substantially no oxygen mixedtherewith when the soybean milk is filled into the pack container.

A third aspect of the present invention provides a soybean milkmanufacturing method which is characterized by comprising the steps ofimmersing soybeans in water for a predetermined time; grinding the thusobtained swelled soybeans; extracting soybean protein by boiling thethus obtained ground soybeans with superheated steam evaporating fromwater processed by an oxygen removing treatment and containing little orno oxygen (hereinafter, referred to as superheated oxygen-free-steam)for a predetermined time; obtaining boiled bean juice containing theextracted soybean protein; and manufacturing soybean milk in which thesoybean protein is suspended and which contains oxygen dissolved thereinin an amount of 5 ppm or less by separating an okara as a solid matterfrom the thus obtained boiled bean juice without cooling it in anoxygen-free environment.

It is preferable that the oxygen in the superheated oxygen-free-steamand the oxygen dissolved in the soybean milk are not substantiallycontained.

A fourth aspect of the present invention provides a soybean milk packmanufacturing method which is characterized by comprising the steps ofimmersing soybeans in water for a predetermined time; grinding the thusobtained swelled soybeans; extracting soybean protein by boiling thethus obtained ground soybeans with superheated oxygen-free-steam for apredetermined time; obtaining boiled bean juice containing the extractedsoybean protein; manufacturing soybean milk in which the soybean proteinis suspended and which contains oxygen dissolved therein in an amount of5 ppm or less by separating an okara as a solid matter from the thusobtained boiled bean juice without cooling it in an oxygen-freeenvironment; filling the thus manufactured soybean milk into a packcontainer preferably in an oxygen-free environment without heating itand without cooling it; and thereafter cooling and storing the soybeanmilk pack at a temperature of 1° C.-10° C. or less.

It is preferable that oxygen in the superheated oxygen-free-steam, theoxygen dissolved in the soybean milk and oxygen mixed when the soybeanmilk is filled into the pack container are not substantially contained.

A fifth aspect of the present invention provides a soybean curdmanufacturing method which is characterized by comprising the steps offilling the soybean milk manufactured by the soybean milk manufacturingmethod of the third aspect of the present invention into a soybean curdmanufacturing insulated container or tearing open the soybean milk packmanufactured by the soybean milk pack manufacturing method of the fourthaspect of the present invention and filling the soybean milk containedtherein into the soybean curd manufacturing insulated container; addinga suitable amount of a coagulant to the soybean milk in the soybean curdmanufacturing insulated container and sufficiently mixing the coagulantwith the soybean milk; disposing non-corrosive electrodes in the mixedsolution of the coagulant and the soybean milk on both the sides of thesoybean curd manufacturing insulated container; passing an alternatingcurrent between the non-corrosive electrodes under such conditions thatno electrolysis occurs in the mixed solution; and manufacturing asoybean curd by coagulating the soybean protein by heating the mixedsolution from passing of the alternating current.

It is preferable that the ground soybeans are boiled with thesuperheated oxygen-free-steam to obtain boiled bean juice formanufacturing the soybean curd by the steps of using a caldroncomprising a caldron main body having a charge port disposed in thevicinity of an end thereof and a discharge port disposed in the vicinityof the other end thereof with both the ends closed, at least a steaminjection pipe installed in the caldron main body and having a pluralityof steam injection ports disposed along the longitudinal direction ofthe caldron main body and a steam generation means, wherein thesuperheated oxygen-free-steam is injected from the steam injection portsin an inclined direction and direction from radial direction of thesteam injection pipe so as to be supplied in a circumferential directionin the caldron main body; charging the ground soybeans through thecharge port; supplying the superheated oxygen-free-steam generated bythe steam generation means to the steam injection pipe; injecting thesuperheated oxygen-free-steam from the plurality of steam injectionports of the steam injection pipe and supplying the same in acircumferential direction of the caldron main body; extracting soybeanprotein by mixing the ground soybeans with the superheatedoxygen-free-steam and stirring the mixture of them while fluidizing theground soybeans and boiling the ground soybeans; and discharging theboiled bean juice containing the extracted soybean protein through thedischarge port.

It is preferable that the superheated oxygen-freesteam injected from theplurality of steam injection ports of the steam injection pipe aresupplied in the same circumferential direction in the caldron main body,or the superheated oxygen-free-steam injected from a portion of theplurality of steam injection ports and the superheated oxygen-free-steaminjected from the remaining portion thereof are supplied in oppositecircumferential directions in the caldron main body, respectively.

It is preferable that the caldron further comprises a cooling meansdisposed to the caldron main body on a discharge side thereof forcooling the boiled raw material and the remaining steam in the caldronmain body.

It is preferable that the steam generation means includes an oxygenremoving means.

It is preferable that the superheated oxygen-free-steam is superheatedsteam substantially containing no oxygen.

Further, it is preferable that the coagulant is nigari.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing a flow of a soybean curd manufacturingsystem to which a soybean curd manufacturing method according to thepresent invention is applied.

FIG. 2 is a front elevational view of an embodiment a caldron used in aboiling step in soybean milk manufacturing method according to thepresent invention.

FIG. 3 is a longitudinal sectional view of the caldron shown in FIG. 2.

FIG. 4 is a front elevational view of a steam injection pipe used in thecaldron shown in FIG. 3.

FIG. 5 is a sectional view of a steam injection pipe taken along theline III—III shown in FIG. 4.

FIG. 6 is a sectional view of the steam injection pipe taken along theline IV—IV shown in FIG. 4.

FIG. 7 is a sectional view of the caldron taken along the line VI—VIshown in FIG. 2.

FIG. 8 is a front elevational view of another embodiment of the steaminjection pipe used in the caldron shown in FIG. 2.

FIG. 9 is a sectional view of an embodiment of a solution heatingapparatus for soybean curd manufacturing used in soybean milkcoagulating process in the soybean curd manufacturing method accordingto the present invention.

BEST MODE OF CARRYING OUT THE INVENTION

Soybean milk, soybean milk packs, methods of manufacturing the soybeanmilk and the soybean milk packs and a method of manufacturing soybeancurd by using them according to the present invention will be describedbelow in detail with reference to preferable embodiments shown in theaccompanying drawings.

First, soybean milk of a first aspect of the present invention ischaracterized in that the content of oxygen dissolved in the soybeanmilk is 5 ppm or less or preferably substantially 0 ppm, that is, nooxygen is contained therein in a state that soybean protein, which isobtained by separating a solid matter such as an okara and the like frombean juice (boiled bean juice), is suspended in the soybean milk, thatis, in a state that the soybean milk is not processed by a heattreatment such as a high temperature sterilizing treatment or the like.Incidentally, ordinary water contains oxygen of 8-10 ppm. Theconcentration of the soybean protein in the soybean milk of the presentinvention is not particularly limited, it is preferably 12% or more,more preferably 13% or more in a state that it is obtained by separatingthe solid matter such as the okara and the like from the bean juice(boiled bean juice), that is, in a state that the heat treatment such asa concentration treatment and the like is not carried out. While theupper limit of the concentration of the soybean protein is notparticularly limited, it is preferably as high as possible. However, theconcentration of the soybean protein which can be actually achievedwithout subjecting the soybean protein to the concentration treatment isabout 15% to 16%.

The soybean milk of the present invention has the deliciousness andsweet taste of soybeans, freshness and good taste, smell anddeliciousness as a fresh soybean milk and is excellent as a raw materialof a tasteful soybean curd having a good taste and deliciousness withoutporosities caused by dissolved oxygen. In addition to the above, thesoybean milk is tasteful even if it is drunk as a drink, and can bedrunk even by a person with atopic dermatitis and allergy symptoms inplace of a cow's milk.

Note that when the soybean milk obtained by separating the okara fromthe bean juice is processed by the heat treatment such as the hightemperature sterilizing treatment, the concentration treatment and thelike, the dissolved oxygen can be reduced or made to substantially 0 ppmas well as the concentration thereof can be increased. However, when thesoybean milk is processed by the heat treatment, their freshness, taste,smell, deliciousness and the like as the soybean milk are lost. Inaddition, when a soybean curd is manufactured from the thus heat-treatedsoybean milk, the taste and deliciousness thereof are lost. Thus, theheat treatment is not preferable to the soybean milk because a tastefulsoybean curd cannot be manufactured therefrom.

When the soybean milk of the present invention is not in contact with anoxygen-containing-atmosphere such as air and the like and furtherpreferably stored at a low temperature in the temperature range 1-10°C., it can be stored while keeping a good taste, flavor anddeliciousness in a fresh state, that is, without deteriorating the highquality thereof for one week from the date it was manufactured when theamount of oxygen dissolved in the soybean milk is 5 ppm or less, forthree weeks when the amount of oxygen dissolved therein is 2 ppm or lessand for one month when the amount of oxygen dissolved therein issubstantially 0 ppm. Note that when the soybean milk of the presentinvention is stored in the more preferable temperature range of 2-5° C.,it can be stored a longer period of time.

The soybean milk packs of a second aspect of the present invention arecharacterized in that the soybean milk of the first aspect of thepresent invention is filled into pack containers in such a manner thatmixed oxygen in the soybean milk packs is preferably made tosubstantially 0 ppm, that is, no oxygen is contained therein in a statethat soybean protein which is obtained by separating a solid matter suchas an okara and the like from bean juice (boiled bean juice) issuspended in the soybean milk of the first aspect of the presentinvention, that is, in a state that the soybean milk is neitherprocessed by a high temperature sterilizing treatment nor cooled; andthat the soybean milk packs are stored at a low temperature of 1-10° C.and more preferably 2-5° C.

When the soybean milk packs of the present invention are stored at a lowtemperature in the temperature range of 1-10° C. and more preferably2-5° C., they can be stored while keeping a good taste, flavor anddeliciousness, that is, without deteriorating the quality thereof forone week from the date they were manufactured when the amount of oxygendissolved in the soybean milk and the oxygen mixed with the packs is 5ppm or less, for three weeks when the amount of them is 2 ppm or lessand for one month when the amount of them is substantially 0 ppm.

The pack containers into which the soybean milk of the present inventionis filled are not particularly limited so long as they are packcontainers used for foodstuffs and are not harmful at a high temperatureof 50-99° C., at a low temperature of 1-10° C. and at an intermediatetemperature therebetween. However, pack containers such as antibactrialpack containers to which oxygen is not permeable are preferable and, forexample, polyolefin resin containers and bags, pack containers and bagson which a polyolefin resin film is coated and vinyl containers can beexemplified.

Not only the soybean milk packs of the present invention can be storedfor a long period of time but also contents of the containers issuitable for easy transportation. Therefore, the soybean milk packs canbe supplied to ordinary homes and eating houses as well as to specialitysoybean curd manufacturers as a material of a tasteful soybean curdwithout a nest where germs breed and without porosities which are causedby dissolved oxygen or as a tasteful soybean milk drink which can bedrunk as it is. Further, the soybean milk packs can be stored in aconsumer refrigerator as well as in a commercial-use refrigerator.

The soybean milk and the soybean milk packs can be manufactured bysoybean milk and soybean milk packs manufacturing methods of a third andfourth aspects of the present invention, in a soybean curd manufacturingsystem to which a soybean curd manufacturing method of a fifth aspect ofthe present invention is applied. The above respective methods andsystem will be shown below.

FIG. 1 schematically shows a view explaining the soybean curdmanufacturing system to which the soybean milk, soybean milk packs andsoybean curd manufacturing methods of the third, fourth and fifthaspects of the present invention are applied.

First, the soybean milk manufacturing method of the third aspect of thepresent invention will be performed in the soybean curd manufacturingsystem of the present invention.

In the soybean milk manufacturing method, first, soybeans as a rawmaterial are immersed in water for a predetermined time and swelled.Next, the thus obtained swelled soybeans are ground. A method and meansfor grinding the swelled soybeans are not particularly limited and aconventionally known grinding method and means may be used. While thesoybeans immersed in the water are ground here, the present invention isnot limited thereto and soybeans ground in a dry state may be swelled bybeing immersed in water.

The obtained ground soybeans are boiled for a predetermined time withsuperheated steam evaporating from water subjected to an oxygen removingtreatment and containing substantially no oxygen and soybean protein isextracted therefrom without losing the flavor and deliciousness thereof,whereby bean juice (boiled bean juice) of high quality containing theextracted soybean protein is obtained. Incidentally, since ordinarywater contains oxygen in the amount of 8-10 ppm, it is preferable toproduce steam from water from which oxygen is removed as much aspossible. The bean juice of high quality can be successivelymanufactured for the first time by a novel bean-juice-manufacturingcaldron shown in FIG. 2 to FIG. 8.

While the swelled and ground soybeans are used as they are as the rawmaterial of bean juice to be charged into the bean-juice-manufacturingcaldron here, the present invention is not limited thereto. That is, theswelled and ground soybeans may be preparatorily heated to promote theextraction of soybean protein in the bean-juice-manufacturing caldron sothat the soybeans can be easily boiled or soybeans crushed or ground ina dry state may be directly charged into the bean-juice-manufacturingcaldron without being mixed with water and being swelled.

A temperature at which the superheated oxygen-free-steam used to boilthe material of bean juice is supplied is not particularly limited solong as the soybean protein can be extracted at the temperature and itis ordinarily 110° C. or higher. However, it is preferable to set thetemperature to 150-190° C. when it is desired to obtain thedeliciousness of soybeans and to 180-190° C. when it is desired toparticularly increase the deliciousness of soybeans. However, it iscontemplated that an excessively high temperature changes the nature ofextracted soybean protein, the temperature of steam is preferably set to110-120° C. in an ordinary boiling and the temperature may be suitablyset in accordance with soybeans condition and a desired level of taste.

A pressure at which the superheated oxygen-free-steam is supplied is notparticularly limited so long as soybeans can be boiled at the pressureuniformly. However, it is preferable to set the pressure to, forexample, 5-7 kg/cm2 for the effective boiling of soybeans.

In this manner, bean juice of high quality, which has been uniformly andsufficiently boiled without unevenness can be obtained by the novelbean-juice-manufacturing caldron.

The novel bean-juice-manufacturing caldron used in the boiling step ofthe present invention will be described later.

The bean juice obtained by using the novel bean-juice-manufacturingcaldron is discharged therefrom at a high temperature of 90-99° C. Then,an okara as a solid matter is separated from the heated bean juicewithout cooling in the temperature range of, for example, 80-95° C.preferably in an oxygen-free state, whereby the soybean milk of thefirst aspect of the present invention can be manufactured, that is,soybean milk having soybean protein suspended therein can bemanufactured. At the time, an amount of the oxygen dissolved in thesoybean protein is 5 ppm or less and preferably substantially 0 ppm (nodissolved oxygen contained).

A separating method and means used in the process for separating theokara as the solid matter from the bean juice of high quality obtainedby the present invention are not particularly limited and aconventionally known separating method and means and a conventionallyknown filtering method and means may be used. However, it is preferablethat the separation be performed in a substantially oxygen-freeenvironment.

Since the thus obtained soybean milk contains little or substantially nodissolved oxygen even if it is not processed by a heat treatment such asa high temperature sterilizing treatment and the like, no germs breedtherein and the soybean milk can be stored for a long time while keepingits freshness without the deterioration of the taste and deliciousnessthereof. Further, the concentration of the soybean protein in theobtained soybean milk is higher than that in a conventional soybean milkeven if it is not subjected to a heat treatment such as a concentrationtreatment. That is, the concentration therein reaches 13-16% in contrastto the concentration in the conventional soybean milk of 10-12%.

The soybean milk manufacturing method of the third aspect of the presentinvention is basically arranged as described above.

Next, the soybean milk pack manufacturing method of the fourth aspect ofthe present invention will be described.

In the soybean milk pack manufacturing method of the aspect, the soybeanmilk of the first aspect of the present invention is manufacturedaccording to the soybean milk manufacturing method of the third aspectof the present invention. Accordingly, the description of the process inwhich the soybean milk is manufactured is omitted.

The soybean milk manufactured according to the soybean milkmanufacturing method of the third aspect of the present invention isfilled into pack containers while maintaining a temperature of 80-95° C.preferably in an oxygen-free environment in which no oxygen is mixed andpreferably no oxygen is substantially contained without being processedby a heat treatment such as a high temperature sterilizing treatment, aconcentration treatment and the like and by a cooling treatment.

The soybean milk packs of the second aspect of the present invention canbe manufactured as described above.

In the obtained soybean milk packs, even if soybean milk is filled intopack containers in an oxygen containing environment and germs are mixedwith the soybean milk, they are sterilized at high temperature becausethe soybean milk in the pack containers is at a high temperature of80-95° C. just after it is filled thereinto. Further, even if germsremain in the soybean milk without being perfectly sterilized, theycannot breed because the oxygen dissolved in the soybean milk packs andthe oxygen mixed with the soybean milk when it is filled into the packcontainers is little or substantially zero. Accordingly, the soybeanmilk packs of the second aspect of the present invention can be storedfor a long time.

In the soybean milk pack manufacturing method of the fourth aspect ofthe present invention, it is preferable to cool or preferably rapidlycool the soybean milk just after it is filled into the pack containersand to store it at 1-10° C. or less, preferably at 1-5° C. and morepreferably at 2-5° C. With this treatment, even if germs, which are notsterilized even by the filling of the soybean milk at high temperature,remain in the soybean milk in the soybean milk packs of the presentinvention, they are sterilized at low temperature while the soybean milkis stored at a low temperature. Further, even if germs remain in thesoybean milk without being sterilized at low temperature, they neitherbreeds nor is active because the oxygen dissolved in or mixed with thesoybean milk is little or do not substantially exist.

Therefore, the soybean milk packs of the present invention can be storedfor a long period of time.

In the manner as described above, the soybean milk packs, which can bestored for a long period of time, can be manufactured. The soybean milkpacks can be distributed and transported to homes and eating houses aswell as to speciality soybean curd manufacturers in accordance withapplication thereof and can be easily stored thereby.

The soybean milk pack manufacturing method of the fourth aspect of thepresent invention is basically arranged as described above.

Next, the soybean curd manufacturing method of the fifth aspect of thepresent invention will be described.

In the soybean curd manufacturing method of the aspect, the soybean milkof the first aspect of the present invention is manufactured accordingto the soybean milk manufacturing method of the third aspect of thepresent invention, and the soybean milk packs of the second aspect ofthe present invention are manufactured according to the soybean milkpack manufacturing method of the fourth aspect of the present invention.Therefore, the description of the process in which the soybean milk ismanufactured and description of the process in which the soybean milkpacks are manufactured are omitted.

The soybean milk of the first aspect of the present invention, which ismanufactured according to the soybean milk manufacturing method of thethird aspect of the present invention and stored at low temperature whennecessary, is directly charged into the soybean curd manufacturinginsulated container of a solution heating apparatus for soybean curdmanufacturing. Otherwise, the soybean milk packs of the second aspect ofthe present invention, which are manufactured according to the soybeanmilk pack manufacturing method of the fourth aspect of the presentinvention, distributed, and stored at low temperature when necessary,are tore open and the soybean milk contained in the packs is chargedinto the soybean curd manufacturing insulated container.

Subsequently, the soybean milk in the soybean curd manufacturinginsulated container is added with an appropriate amount of a coagulant,preferably calcium chloride or nigari mainly composed of calciumchloride and sufficiently mixed therewith. After both of them aresufficiently mixed, the non-corrosive electrodes of the solution heatingapparatus for soybean curd manufacturing are immersed in the mixedsolution of the soybean milk and the coagulant on both the sides of thesoybean curd manufacturing insulated container.

Next, an alternating current is passed between the non-corrosiveelectrodes from the power supply of the solution heating apparatus forsoybean curd manufacturing under such conditions that no electrolysisoccurs in the mixed solution of the soybean milk and the coagulant,whereby the mixed solution is heated and soybean protein is coagulatedso that a soybean curd can be manufactured.

The soybean curd manufacturing insulated container, the non-corrosiveelectrodes and the solution heating apparatus for soybean curdmanufacturing having the power supply, which are used in the process forcoagulating the soybean milk, will be described later.

In the aspect, it is preferable to charge a cooled soybean milk of lowtemperature into the soybean curd manufacturing insulated container. Thereason is that since the soybean milk of the present invention issoybean milk of high quality without being unevenly boiled, when itstemperature is high, the condensing and coagulating reaction of thesoybean milk with the coagulant is promptly performed and thus thenigari cannot be uniformly mixed with all the soybean milk in thecontainer. A mixing quantity of the soybean milk of the presentinvention with the nigari is not particularly limited and a conventionalmixing quantity can be employed. For example, when soybean milk has aconcentration of 12-15%, it is preferable to mix a nigari of about 3-4%as a concentration of magnesium chloride. Further, as to a heatingtemperature and a heating time, when the initial temperature of soybeanmilk is about 10° C., the soybean milk can be coagulated and made to asoybean curd in about 15 minutes from start of heating because anecessary heating temperature is 75-90° C.

As described above, according to the soybean curd manufacturing methodof the fifth aspect of the present invention, a fresh, tasteful,moderate and delicious soybean curd of high quality without porositiesformed therein which is mild on the tongue and has a good water holdingproperty can simply manufactured even by a nonprofessional in ordinaryhomes and eating houses, in addition to speciality soybean curdmanufacturers, by using the soybean milk and soybean milk packs of highquality of the present invention. As a result, a just cooked freshsoybean curd can be supplied to the table.

Since the obtained soybean curd contains little or substantially nodissolved oxygen even if it is manufactured by a nonprofessional, noporosity is formed therein.

While the soybean curd manufacturing insulated container, and thesolution heating apparatus for soybean curd manufacturing having thenon-corrosive electrodes and the power supply are used in the processfor coagulating the soybean milk, the present invention is not limitedthereto and any heating system may be employed so long as the mixedsolution of the soybean milk and the coagulant in the container can bedirectly heated different from the conventional system of heating itfrom the outside, and for example, an electromagnetic heating system, ahigh frequency heating system, and the like are applicable.

The soybean curd manufacturing method of the fifth aspect of the presentinvention is basically arranged as described above.

Next, the novel bean-juice-manufacturing caldron used in the boilingprocess of the soybean milk, soybean milk packs and soybean curdmanufacturing methods of the third, fourth and fifth aspects of thepresent invention will be described below.

FIG. 2 is a front elevational view of an embodiment of thebean-juice-manufacturing caldron applied to the boiling process of thepresent invention. A bean-juice-manufacturing caldron installedvertically will be described here as a typical example, thebean-juice-manufacturing caldron of the present invention is not limitedthereto.

The bean-juice-manufacturing caldron 10 shown in FIG. 2 comprises acylindrical caldron main body 12 installed vertically, a steam injectionpipe 14 (or 15) installed upright in the caldron main body 12 at thelower central portion thereof, an annular water-cooling jacket 16 as acooling means disposed around the outer periphery of the caldron mainbody 12 at the upper portion thereof, an orifice plate 18 disposed inthe caldron main body 12 between the steam injection pipe 14 (or 15) andthe water-cooling jacket 16 and a steam generation means 20 disposedexternally of the caldron main body 12 for supplying superheated steaminto the steam injection pipe 14 (or 15).

The bean-juice-manufacturing caldron 10 shown in FIG. 2 is arranged suchthat various kinds of steam injection pipes can be replaceably installedthereto. For example, the steam injection pipe 14 having a structureshown in FIG. 4 and the steam injection pipe 15 shown in FIG. 8 whichwill be described later, and other steam injection pipes having astructure other than the above can be replaceably used for variousapplications such as main boiling, additional boiling and other boiling.

First, the bean-juice-manufacturing caldron 10 shown in FIG. 3 to whichthe steam injection pipe 14 shown in FIG. 4 is applied will be describedbelow.

FIG. 3 is a longitudinal sectional view of the bean-juice-manufacturingcaldron 10 shown in FIG. 2.

In FIG. 2 and FIG. 3, the caldron main body 12 boils a raw material G ofbean juice and the heated material thereof (which are hereinaftergenerically referred to by the term “material of bean juice”) with thesteam S injected from the steam injection pipe 14 (refer to FIG. 5 andFIG. 6). The caldron main body 12 is composed of a cylindrical stainlesssteel pipe with both the ends thereof formed to a semi-spherical shapeand closed and has a charge port 22 disposed to the semi-sphericalbottom portion thereof and a discharge port 24 disposed to thesemi-spherical top portion thereof. The material of bean juice ischarged through the charge port 22. In the caldron main body 12, afterthe raw material G of bean juice is boiled with the steam S injectedfrom the steam injection pipe 14, the steam S is cooled by thewater-cooling jacket 16 in the upper portion of the caldron main body 12and liquefied and condensed so that the pressure thereof is reduced. Asdescribed above, the steam injected in a circumferential direction fromthe steam injection pipe 14 and fluidizes the raw material G of beanjuice in the lower portion of the caldron main body 12 and then thesteam is cooled and condensed in the upper portion of the caldron mainbody 12, so the continuously charged raw material G of bean juice isfluidized from the lower charge port 22 to the upper discharge port 24while being boiled so that it smoothly move upward spirally. Thus, thebean juice, which has been sufficiently and uniformly boiled, can besuccessively and smoothly discharged from the discharge port 24.

The steam injection pipe 14 injects superheated steam into the caldronmain body 12 to boil the raw material G of bean juice charged throughthe charge port 22 in the caldron main body 12 and to move it in thecircumferential direction in the caldron main body 12, that is, to moveupward it spirally therein. In the illustrated example, the steaminjection pipe 14 is composed of a stainless steel pipe installedupright in the caldron main body 12 from the bottom to a central portionthereof. As shown in FIG. 4, the upper end of the steam injection pipe14 is closed and a plurality of injection ports 26 and 28 are formedalong each of the same straight lines extending in the verticaldirection of the steam injection pipe 14.

As shown in FIG. 5, a lower deflector 30 is mounted in the vicinity ofthe lower injection ports 26 of the steam injection pipe 14 on the leftside thereof for changing the direction of the steam S injected from theinjection ports 26 so that they are directed from a radial direction toa direction inclined rightward in the figure, for example, so that theyare directed rightwards in a tangential direction. The lower deflector30 is mounted to the steam injection pipe 14 with the left side portionthereof attached to the steam injection pipe 14 in the vicinity of theleft side of the lower injection ports 26 in the figure such that itcovers the lower injection ports 26 obliquely, that is, in a tangentialdirection in the illustrated example at a position near to them. Incontrast, as shown in FIG. 6, an upper deflector 32 is mounted to thestream injection pipe 14 in the vicinity of the right side of the upperinjection ports 28 of the steam injection pipe 14 on the right sidethereof so as to cover the upper injection ports 28 obliquely, that is,in a tangential direction in the illustrated example at a position nearto them. As a result, the upper deflector 32 deflects the steam Sinjected from the upper injection ports 28 so that the direction thereofis deflected from a radial direction to a direction inclined leftwardsso that it is directed, for example, leftwards in a tangentialdirection.

As described above, the lower deflector 30 and the upper deflector 32,which are mounted on the steam injection pipe 14 in an oppositedirection, permits the steam from the injection ports 26 and 28, whichare located at the upper half portion and the lower half portion of thesteam injection pipe 14, to be injected in opposite circumferentialdirections. As a result, in the caldron 10 of the illustrated example,the steam S injected from the upper injection ports 28 of the steaminjection pipe 14 can be caused to come into contact with the rawmaterial G of bean juice sufficiently and uniformly and the heat of thesteam can be sufficiently transmitted thereto, whereby the raw materialG of bean juice is uniformly and sufficiently boiled. Therefore, sinceall the steam S reaching the upper portion of the caldron main body 12sufficiently lower their temperature and a part or all of the steam Scan be liquefied and condensed, steam S, which remain residually at hightemperature while keeping a sufficient quantity of heat capable ofboiling the raw material G of bean juice, can be almost eliminated.

Further, as shown in FIGS. 2, 3 and 4, the lower end of the steaminjection pipe 14 is also closed, and a steam supply pipe 34 isconnected perpendicular to the steam injection pipe 14 in the vicinityof the lower end thereof. The steam supply pipe 34 is fixed to amounting section 36 with a steam supply port 36 a located at a lowerportion of the caldron main body 12 so as to extend to the outsidethrough the caldron main body 12. The steam supply pipe 34 extending tothe outside of the caldron main body 12 is connected to the steamgeneration means 20 such as a boiler or the like for generatingsuperheated steam.

The water-cooling jacket 16 is disposed around the outer peripheral wallof the caldron main body 12 at the upper portion thereof, formed to anannular shape and has closed upper and lower end portions. The interiorof the water-cooling jacket 16 is arranged as an annular cooling chamber38 which can be filled with a cooling water. Further, a cooling waterdischarge port 40 and a cooling water charge port 42 are disposed to thewater-cooling jacket 16 on the upper and lower sides thereof,respectively. With this arrangement, the water-cooling jacket 16sufficiently liquefies and condenses the steam S whose temperature islowered through the function thereof for sufficiently boiling the rawmaterial G of bean juice and making it to bean juice, to thereby lowerthe pressure of the upper portion of the caldron main body 12 andpreferably to provide a pressure reduced atmosphere in the upper portionthereof.

The provision of the water-cooling jacket 16 can sufficiently liquefyand condense the steam reaching the upper portion of the caldron mainbody 12 and having lowered temperature. In addition, even if hightemperature remaining steam reaches the upper portion of the caldronmain body 12, it can be sufficiently cooled, liquefied and condensed bythe water-cooling jacket 16. Thus, such an adverse effect of hightemperature remaining steam, which arises in a conventional caldron, canbe eliminated that it stays in the upper portion of the caldron mainbody 12 as it is, increases the pressure of the upper portion thereof,and pushes out the raw material of bean juice into the discharge port 24of the caldron main body 12 in a quantity larger than necessary, therebymaking it impossible to properly control the feed of the raw material ofbean juice.

The orifice plate 18 prevents the steam reaching the upper portion ofthe caldron main body 12 with their temperature lowered from beingdirectly discharged through the discharge port 24 so that they can besufficiently cooled with the water-cooling jacket 16 by being stayed inthe caldron main body 12. Thus, the orifice plate 18 sufficientlyliquefies and condenses the steam with its temperature lowered as wellas the remaining steam as well as causes the bean juice to come intocontact with the inner wall surface, which is cooled with thewater-cooling jacket 16, of the caldron main body 12 at the upperportion thereof, thereby effectively cooling them. The orifice plate 18is disposed in the vicinity of the lower end of the water-cooling jacket16 mounted to the upper portion of the caldron main body 12, and hasfour orifices (openings) 18 a formed around the periphery thereof in theillustrated example.

With this arrangement, even if remaining steam having a quantity of heatcapable of boiling the raw material G of bean juice reach the upperportion of the caldron main body 12 and stay therein while keeping theirhigh temperature, in addition to steam with its temperature lowered, theremaining steam and the boiled bean juice are dammed out by the orificeplate 18 together, stay below the orifice plate 18 for a predeterminedtime and are sufficiently cooled with the water-cooling jacket 16. As aresult, almost all or preferably all the steam is liquefied andcondensed even if the remaining steam exists. In contrast, the upwardmovement of the boiled bean juice is prevented by the orifice plate 18and passes through the orifices 18 a on the periphery of the orificeplate 18. As a result, the bean juice passed through the orifices 18 ais forcibly caused to contact with the cooling inner wall surface of thecaldron main body 12 at the upper portion thereof so that it is not onlycooled efficiently but also unliquefied steam, even if they arecontained in the bean juice, are instantly liquefied and condensed.Therefore, the steam in the caldron main body 12 is not directlydischarged through the discharge port 24.

The steam generation means 20 is used to generate superheated steamwhich will be supplied to the steam injection pipe 14 installed in thecaldron main body 12 and is not particularly limited. Thus, aconventionally known boiler and the like may be used. However, it ispreferable that the steam generation means 20 includes an oxygenremoving means 44 for making the superheated steam to be supplied to thesteam injection pipe 14 to superheated steam which preferably containsno oxygen substantially (hereinafter, referred to as superheatedoxygen-free-steam).

In the illustrated example, the provision of the oxygen removing means44 with the steam generation means 20 permits superheatedoxygen-free-steam to be supplied to the steam injection pipe 14 and tobe injected into the caldron main body 12 through the plurality ofinjection ports 26 and 28. The raw material G of bean juice in thecaldron main body 12 can be thereby boiled with the superheatedoxygen-free-steam that it can be boiled with superheatedoxygen-free-steam so as not to be oxidized. Therefore, the quantity ofthe oxygen dissolved in the liquid component of the thus obtained beanjuice can the minimized. As a result, little or preferably no oxygen isdissolved in the soybean milk of the present invention, which isobtained by separating a solid matter (okara) from the thus obtainedbean juice, whereby the soybean milk can be stored in a fresh state fora period of time greatly longer than a conventional soybean milk.

In the illustrated example, the oxygen removing means 44 provided withthe steam generation means 20 is not particularly limited so long as itcan eliminate the substantial content of oxygen from steam. That is,employed as the oxygen removing means 44 may be a means for reducingpressure so that air and oxygen is not mixed into, for example, thesteam generating unit of the steam generation means 20 as well as ameans for reducing in advance the pressure of the water to be suppliedto the steam generating unit of the steam generation means 20 or heatingthe water while reducing the pressure thereof so as to remove the oxygendissolved therein, a means for removing the oxygen dissolved in water tobe supplied to the steam generating unit by adding an oxygen removingagent to the water, and any other conventionally known oxygen removingmeans. In addition, any conventionally known oxygen removing methods maybe employed.

The caldron of the illustrated example is basically arranged asdescribed above. Operation of the caldron of the illustrated example andthe boiling process in the soybean milk manufacturing method of thepresent invention will be described with reference to thebean-juice-manufacturing caldron shown in FIG. 2 to FIG. 7.

First, when superheated oxygen-free-steam is supplied from the steamgeneration means 20 into the steam injection pipe 14, the steam injectedfrom the injection ports 26 in an radial direction is deflected by thelower deflector 30 counterclockwise in a circumferential direction inthe caldron main body 12 in the lower portion of the steam injectionpipe 14 so that the steam flow round backward of the injection ports 26.In contrast, the steam injected from the injection ports 28 in an radialdirection is deflected by the upper deflector 32 clockwise in acircumferential direction in the caldron main body 12 in the upperportion of the steam injection pipe 14 so that the steam flow roundbackward of the injection ports 28.

At the time, when a raw material of bean juice is supplied by a feedpump (not shown) or the like through the charge port 22 located at thelower portion of the caldron main body 12, the raw material of beanjuice in the vicinity of the lower portion of the steam injection pipe14 is moved counterclockwise in a circumferential direction by thesteam, which are injected from the plurality of injection ports 26 and28 of the steam injection pipe 14 and deflected rightward in the figureby the lower deflector 30. In contrast, the raw material of bean juicein the vicinity of the upper portion of the steam injection pipe 14 ismoved clockwise in a circumferential direction by the steam deflectedleftward in the figure by the upper deflector 32. The raw material ofbean juice, which is not in contact with the previously injected steam,is successively moved to the portion of the caldron main body 12 wherenew steam is injected from the injection ports 26 and 28 and comes intocontact with the new steam having high thermal energy and high motionenergy. In this manner, since the steam moves upward in the caldron mainbody 12 spirally, it stays in the caldron main body 12 for a long timewhile being in uniform contact with the raw material of bean juice. Atthe same time, in the vicinity of the intermediate portion of the steaminjection pipe 14 between the upper portion and the lower portionthereof, the raw material of bean juice moves along a convection currentwhich has opposite directions between the upper portion and the lowerportion of the steam injection pipe 14.

The raw material of bean juice moving counterclockwise in the lowerportion of the steam injection pipe 14 in the caldron main body 12 ismoved upward by a not shown feed pump or the like and made to a complexturbulent flow with its turning direction reversed clockwise, wherebythe steam is further more in good contact with raw material of beanjuice. With this operation, the heat of the steam is uniformly andsufficiently transmitted to the raw material of bean juice. Thus, thesteam is robbed of their heat thereby and liquefied and condensed from agas so that the volume thereof is reduced, by which the pressure in thecaldron main body 12 is lowered. As a result, the raw material of beanjuice is not pushed out through the discharge port 24 by the pressure inthe caldron main body 12 in a quantity larger than necessary to ensurethat it is heated so as not to be cooked unevenly.

Subsequently, in the upper portion of the caldron main body 12, sincethe upward movement of the boiled bean juice and remaining steam (steamkeeping their high temperature may be contained in low temperaturesteam) is prevented by the orifice plate 18, they stay temporarily attheir locations so that the liquefaction and condensation of theremaining steam is promoted. In contrast, the remaining steam stayed bythe orifice plate 18 is forcibly cooled with the cooling water flowingin the annular cooling chamber 38 of the water-cooling jacket 16 andliquefied and condensed from a gas to thereby reduce their volume, bywhich the pressure in the upper portion of the caldron main body 12 islowered. In contrast, the bean juice passing through the orifices 18 aon the periphery of the orifice plate 18 is effectively cooled becauseit is caused to come into forcible contact with the inner wall surfaceof the caldron main body 12 which is cooled with the annular coolingchamber 38 of the water-cooling jacket 16. Thus, the bean juice is notpushed out through the discharge port 24 by the pressure of theremaining steam in the caldron main body 12 in a quantity larger thannecessary.

The thus obtained bean juice is bean juice whose quality is greatlyhigher than that of a conventional bean juice because it is not unevenlycooked by being uniformly and sufficiently boiled with the superheatedoxygen-free-steam, is not oxidized, and contains little or substantiallyno dissolved oxygen. The separation of an okara from the bean juice ofhigh quality results in the very fresh soybean milk of the presentinvention in which concentration of the soybean protein is higher thanthat in a conventional soybean milk and in which little or substantiallyno oxygen is dissolved. Since the thus obtained soybean milksubstantially contains no dissolved oxygen, it can suppress the breedingof germs as mush as possible, whereby a period of time during which thefreshness thereof can be maintained can be greatly extended as comparedwith that of the conventional soybean milk. Thus, the deterioration ofthe taste and deliciousness of the soybean milk can be prevented for alonger period of time as compared with that of the conventional soybeanmilk, whereby the soybean milk of the present invention can be storedlonger than the conventional soybean milk.

The steam injection pipe 14 shown in FIG. 4 is provided with the twodeflectors 30 and 32 for deflecting the flowing directions of the steam,which is injected from the respective injection ports 26 and 28 locatedat the lower portion and the upper portion of the steam injection pipe14, in an opposite direction circumferentially, respectively. However,the present invention is not limited thereto and the steam injected fromthe steam injection pipe may flow in any direction and any means forregulating the flowing direction of the steam may be employed.

For example, the flowing direction of the steam injected from theplurality of steam injection ports may be deflected in the samedirection circumferentially by one deflector or may be deflected in anopposite direction circumferentially using three or more deflectors,respectively. The positions where the plurality of steam injection portsare formed in correspondence to one deflector or to each of two or moredeflectors are not limited to the positions on the same straight linewith respect to each of the deflectors. That is, the steam injectionports may be formed on the same straight line with respect to all of thedeflectors, may be formed by dislocating their positions by apredetermined angle, for example, 90° or 180° in the circumferentialdirection of the steam injection pipe with respect to each of thedeflectors or to each injection port. Further, the steam injection portsmay be disposed at equal intervals or absolutely at random. It isneedless to say that each of deflectors may be provided with each of theinjection ports regardless of that steam injected therefrom flows insame direction or not, or one deflector may be provided with a pluralityof injection ports from which steam is injected in the same direction. Adeflector used here is not limited to the flat deflector of theillustrated example and a deflector which is partly or entirely curvedin the circumferential direction of the caldron main body 12 may beused. A direction in which steam is flown by the deflector is notlimited to a circumferential direction precisely and it may be inclinedupward or downward. While it is preferable to provide deflectors withall the injection ports, some of the injection ports may not be providedwith a deflector. The direction of the holes of the injection portsformed to the steam injection pipe is not limited to the radialdirection and may be inclined. Further, the number and size of theinjection port formed to one steam injection pipe is not particularlylimited and may be suitably selected in accordance with thecharacteristics of the caldron. FIG. 8 shows the steam injection pipe 15with one deflector which is used in the caldron 10 shown in FIG. 2. Thesteam injection pipe 15 has a plurality injection ports 46 formed on thesame straight line extending in an vertical direction. The deflector 48is mounted obliquely on the steam injection pipe 15 near to theinjection ports 46 on the left side thereof in the figure, that is, thesteam injection pipe 15 is mounted so as to cover the injection ports 46in a tangential line in the illustrated example.

In the embodiment shown in FIG. 8, the deflector 48 deflects the steaminjected from the injection ports 46 so that they flow in a directionwhich is inclined rightwards in the figure from a radial direction, forexample, rightwards in a tangential direction. As a result, the steaminjected from the injection ports 46 are deflected by the deflector 48in the direction which is inclined rightwards in the figure from theradial direction and flow counterclockwise in a circumferentialdirection in the caldron main body 12.

When the raw material of bean juice is supplied by the feed pump or thelike through the charge port 22 located at the lower portion of thecaldron main body 12, at the time the steam injection pipe 15 shown inFIG. 8 is installed in place of the steam injection pipe 14 shown inFIG. 4, the steam, which is injected and deflected by the deflector 48,move the raw material of bean juice, which is located in the vicinity ofthe steam injection pipe 15 in the upper and lower portions thereof,counterclockwise in the circumferential direction and move upwardspirally in the caldron main body 12 together with the raw material ofbean juice. As a result, the steam comes into even contact with the rawmaterial of bean juice, stay in the caldron main body 12 for a longertime, and the heat of them is uniformly and sufficiently transmitted tothe raw material of bean juice. Thus, the steam loses their energy andare liquefied from a gas and condensed, thereby reducing their volumeand lowering the pressure in the caldron main body 12 as describedabove. As a result, since it is suppressed that the raw material of beanjuice is pushed out through the discharge port 24 by the pressure in thecaldron main body 12 in a quantity larger than necessary, it is heatedso as not to be unevenly boiled.

In the steam injection pipe 15 arranged as described above, the mixingof the steam with the raw material of bean juice and the fluidizationand stir of the raw material of bean juice by the steam are gentlyperformed as compared those strongly performed by the turbulent flow ofthe steam in the steam injection pipe 14 shown in FIG. 4. Thus, thebean-juice-manufacturing caldron 10 provided with the steam injectionpipe 14 shown in FIG. 4 is preferably used in main boiling, whereas thebean-juice-manufacturing caldron 10 provided with the steam injectionpipe 15 shown in FIG. 8 is preferably used in additional boiling.However, the present invention is not limited thereto and the steaminjection pipe 14 may be used in the additional boiling and the steaminjection pipe 15 may be used in the main boiling.

In the bean-juice-manufacturing caldron 10 of the illustrated example,the deflectors 30, 32 and 46, which are obliquely mounted in thevicinity of the injection ports 26, 28 and 46 of the steam injectionpipe 14 and 15, are used as a means for inclining the directions inwhich the steam from the injection ports is injected. However, thepresent invention is not limited thereto and any means may be used solong as it can make the injecting direction of the steam to thecircumferential direction in the caldron main body 12. For example, theinjection ports may be covered with caps to make the injecting directionof the steam to the circumferential direction in the caldron main body12, nozzles may be attached to the injection ports, or a thick member isused for the steam injection pipe and an injection pipe may be obliquelydrilled to form ports.

As described above, while the steam from the injection ports 26, 28 and46 of the steam injection pipes 14 and 15 are injected in thecircumferential direction in the caldron main body 12, the injectingdirection is not restrictive. That is, the injecting direction may beany one of a clockwise direction and a counterclockwise direction, maybe deflected from a clockwise direction to a counterclockwise directionand vice versa for each of the injection ports or at intervals of a fewinjection ports, or may be set absolutely at random.

In the bean-juice-manufacturing caldron 10 of the illustrated example,the single steam injection pipe 14 or 15 is used as the steam injectionpipe. However, the present invention is not limited thereto and two ormore steam injection pipes may be used. In addition, while it ispreferable that the steam injection pipe used in the present inventionbe formed to the cylindrical shape of the illustrated example, it is notlimited thereto and an elliptic cross sectional pipe, a square crosssectional pipe, a modified cross sectional pipe and the like my be used.Further, the size of the steam injection pipe is not particularlylimited.

In the bean-juice-manufacturing caldron 10 of the illustrated example,while the water-cooling jacket 16 disposed at the upper portion of thecaldron main body 12 is used as the cooling means, the present inventionis not limited thereto and a cooling means itself may not be provided oreven if a cooling means is provided, a conventionally known coolingmeans may be used. For example, a pipe or pipes may be spirally woundaround the upper portion of the caldron main body 12 and cool water suchas well water or the like may be supplied thereto by a pump. Further, acooling medium to be used in the cooling means is not limited to coolwater and any conventionally known refrigerant may be used.

In the bean-juice-manufacturing caldron 10 of the illustrated example,while the single orifice plate 18 having the orifices 18 a formed aroundthe periphery thereof is mounted as an orifice plate for temporalitystaying steam and bean juice, the present invention is not limitedthereto. That is, an orifice plate may not be used at all or two or moreorifice plates may be used. Further, the positions where the respectiveorifices of the orifice plates are formed, the number, size and shape ofthe orifices are not particularly limited and they may be suitablydetermined in accordance with the capability, characteristics and likeof the caldron.

In the bean-juice-manufacturing caldron 10 of the illustrated example,while the steam generation means 20 including the oxygen removing means44 is used as the steam generation means 20, the present invention isnot limited thereto. That is, when bean juice, from which soybean milkwhich need not be stored for a long period of time is manufactured, isproduced, the oxygen removing means 44 need not be necessarily providedand a conventionally known boiler and the like which are not providedwith the oxygen removing means 44 may be used as the steam generationmeans 20. It is needless to say that when soybean milk of the presentinvention which can be stored for a long period of time in a fresh stateis manufactured, the steam generation means 20 must be provided with theoxygen removing means 44.

In the bean-juice-manufacturing caldron 10 of the illustrated example,while the four or more similar bean-juice-manufacturing caldrons 10 areordinarily used by being connected to each other in series, the caldronof the present invention may be used in combination with otherdifferently-constructed caldron.

We requested the measurement of the content of the oxygen dissolved inthe soybean milk, which was obtained by using the caldron describedabove and filtering boiled bean juice resulting from bean juice boiledwith superheated steam (120° C., 5 kg) made from water from which oxygenwas removed by pressure reduction to Japan Environment and SanitaryCenter (address: 5-11, 3-chome, Shirakibaru, Ohnojou-shi, FukuokaPrefecture) Japan Environment and Sanitary Center is an inspectionorganization authorized by the minister of Ministry of Health andWelfare (Ministry of Health and Welfare Ei: No. 923). As a result of themeasurement, an average amount of oxygen dissolved in the soybean milkwas 1.4 ppm. When the soybean milk was filled into a polyethylene bag inan ordinary environment, the quality thereof was not changed even ifthree weeks passed. A soybean curd manufactured from the soybean milkwas heated, it was smooth and no porosity was made therein.

Next, a solution heating apparatus for soybean curd manufacturing usedin the soybean milk coagulating process of the soybean curdmanufacturing method of the fifth aspect of the present invention willbe described below.

FIG. 9 is a sectional view showing an embodiment of the solution heatingapparatus for soybean curd manufacturing applied to the soybean milkcoagulating process of the present invention. However, the presentinvention is not limited thereto.

The solution heating apparatus for soybean curd manufacturing 50 shownin the figure is used in the soybean milk coagulating process formanufacturing a soybean curd. The solution heating apparatus for soybeancurd manufacturing 50 comprises a soybean curd manufacturing insulatingcontainer 52 used for a mixed solution M of soybean milk and acoagulant, two non-corrosive electrodes 54 for passing a current in themixed solution M of the soybean milk and the coagulant in the soybeancurd manufacturing insulating container 52 and a power supply 56 forpassing an alternating current on the two non-corrosive electrodes 54.

The soybean curd manufacturing insulating container 52 is an insulatingcontainer made of synthetic resin for manufacturing a soybean curd bymixing soybean milk charged thereinto with a coagulant such as nigari orthe like and coagulating a mixed solution M of the soybean milk and thecoagulant. A material of the container 52 may be any material so long asit has a durability against a temperature of 75-90° C. as well as aninsulating property, and a synthetic resin having an insulatingproperty, for example, Duracon and the like can be exemplified as thematerial. Further, while the container 52 of the illustrated example hasa rectangular cross sectional shape, the present invention is notlimited thereto and it may have any cross sectional shape.

The non-corrosive electrodes 54 are plate-shaped electrodes disposedalong both the inner walls of the soybean curd manufacturing insulatingcontainer 52. They are immersed in the mixed solution M of the soybeanmilk and the coagulant in the soybean curd manufacturing insulatingcontainer 52 and supply a current thereto so that they generate heat bythemselves. When electrode plates are corroded by electricity at thetime the electrodes 54 are energized, a manufactured soybean curd has astain, for example, a black spot resulting from the corroded electrodeplates. To cope with this problem, the plate-shaped electrodes 54 mustbe made of a material which is not corroded even if it is immersed inthe mixed solution M of the soybean milk and the coagulant and energizedtherein. However, electrodes made of any material may be used so long asthe material satisfies this condition. Steel containing titanium,titanium and the like, for example, are exemplified as the material ofelectrode to be used.

The power supply 56 is an alternating current power supply for passingan alternating current on the two non-corrosive electrodes 54. If asoybean milk is electrolyzed by the current imposed on the non-corrosiveelectrodes 54, a soybean curd cannot be manufactured because soybeanprotein is not condensed and thus cannot be coagulated. To cope withthis problem, the current must be passed under the condition in which noelectrolysis generates. Note that this condition can be also set byrestricting a quantity of current per unit area of soybean milk withwhich the non-corrosive electrodes 54 have contact. As an example, it ispreferable to set the quantity of current to 50 mA/cm2 or less. When theupper limit of the current is set, it is preferable to use aconstant-current device to an alternating current supply power unit tomaintain the current below the upper limit current so as to prevent anexcessive current resulting from the change of an electric resistancedue to heating.

In the soybean curd manufacturing method of the fifth aspect of thepresent invention, the solution heating apparatus for soybean curdmanufacturing 50 is used in the soybean milk coagulating process.Accordingly, a tasteful, sweet-smelling and delicious soybean curd ofhigh quality, in which no porosity is formed and which has a sufficientwater keeping property, can be manufactured in a short time without theneed of any sophisticated expert techniques, that is, even in ordinaryhomes and eating houses, which do not have any skilled soybean curdmanufacturing techniques, using the soybean milk of high quality as araw material such as the soybean milk of the first aspect of the presentinvention and the soybean milk filled into the soybean milk packs of thesecond aspect of the present invention.

Since the solution heating apparatus for soybean curd manufacturing 50used here can uniformly increase temperature without any oscillation, itcan manufacture an elastic soybean curd without any porosity bytightening the binding of soybean protein particles in soybean milk.

A coagulant used in the present invention is not particularly limited,and, for example, calcium chloride, a nigari mainly composed of calciumchloride, calcium sulfate and the like can be exemplified. However,calcium chloride and nigari mainly composed of calcium chloride arepreferably used because they can extract the deliciousness and sweettaste of soybeans and add them to a soybean curd.

The solution heating apparatus for soybean curd manufacturing used inthe soybean milk coagulating process of the soybean curd manufacturingmethod of the fifth aspect of the present invention is basicallyarranged as described above.

While the soybean milk, the soybean milk packs, the manufacturingmethods thereof and the soybean curd manufacturing method using thesoybean milk and soybean milk packs have been described above in detailwith reference to the various embodiments, the present invention is byno means limited to the above embodiments and it goes without sayingthat various improvements and design modifications can be made withinthe range which does not depart from the gist of the invention.

INDUSTRIAL APPLICABILITY

As described above in detail, according to the first aspect of thepresent invention, there can be achieved an effect that soybean milk ofhigh quality can be provided. The soybean milk can be obtained byseparating a solid matter from evenly boiled bean juice of high quality,which is obtained using the novel caldron. The soybean milk is notsterilized at high temperature, substantially contains no oxygendissolved therein or mixed therewith, can be stored while keeping thesweet taste, smell, deliciousness and freshness characteristic tosoybean milk without breeding germs, and undergo less deterioration evenif it is stored. Further, the soybean milk can be not only used as a rawmaterial of soybean curd of high quality but also drunk as it is as adrink.

According to the second aspect of the present invention, there can beachieved an effect for providing soybean milk packs into which thesoybean milk of high quality is filled and which can be stored for along time, and which can be handled easily and supplied to ordinaryhomes and eating houses as well as to speciality soybean curdmanufacturers.

According to the third and fourth aspects of the present invention,there can be achieved an effect that the soybean milk of high qualityand the soybean milk packs into which the soybean milk of high qualityis filled can be stably and reliably manufactured.

According to the fifth aspect of the present invention, there can beachieved an effect a just cooked and fresh soybean curd of high qualitycan be supplied to dining tables. The soybean curd can be manufacturedeasily in a short time by a nonprofessional even in ordinary homes andeating houses, in addition to speciality soybean curd manufacturers,using the soybean milk and soybean milk packs of high quality. The thusmade soybean curd is fresh, tasteful, delicious and mild on the tongueand has a good water keeping property without porosities formed therein.

What is claimed is:
 1. A soybean milk manufacturing method comprisingthe steps of: immersing soybeans in water for a predetermined time toobtain swelled soybeans; grinding the thus obtained swelled soybeans toobtain ground soybeans; boiling the thus obtained ground soybeans withsuperheated steam evaporating from water processed by an oxygen removingtreatment and containing little or no oxygen for a predetermined time toobtain a boiled bean juice containing soybean protein which is extractedfrom the boiled soybeans, the boiled bean juice including a solid matterof the boiled soybeans; and manufacturing soybean milk in which thesoybean protein is suspended and which contains oxygen dissolved thereinin an amount of 5 ppm or less by separating the solid matter from thethus obtained boiled bean juice without cooling it in an oxygen-freeenvironment.
 2. The soybean milk manufacturing method according to claim1, characterized in that the oxygen in the superheated steam and theoxygen dissolved in the soybean milk are substantially zero.
 3. Asoybean milk pack manufacturing method comprising the steps of:immersing soybeans in water for a predetermined time to obtain swelledsoybeans; grinding the thus obtained swelled soybeans to obtain groundsoybeans; boiling the thus obtained ground soybeans with superheatedsteam evaporating from water processed by an oxygen removing treatmentand containing little or no oxygen for a predetermined time to obtainboiled bean juice containing soybean protein which is extracted from theboiled soybeans, the boiled bean juice including a solid matter of theboiled soybeans; manufacturing soybean milk in which the soybean proteinis suspended and which contains oxygen dissolved therein in amount of 5ppm or less by separating the solid matter from the thus obtained boiledbean juice without cooling it in an oxygen-free environment; and fillingthe thus manufactured soybean milk into a pack container without heatingit and without cooling it.
 4. The soybean milk pack manufacturing methodaccording to claim 3, characterized in that after the filling step isperformed, the soybean milk pack is cooled and stored at a temperatureof 1° C.-10° C. or less.
 5. The soybean milk pack manufacturing methodaccording to claim 3, characterized in that oxygen in the superheatedsteam, the oxygen dissolved in the soybean milk and oxygen mixed whenthe soybean milk is filled into the pack container are substantiallyzero.
 6. A soybean curd manufacturing method comprising the steps of:immersing soybeans in water for a predetermined time to obtain swelledsoybeans; grinding the thus obtained swelled soybeans to obtain groundsoybeans; boiling the thus obtained ground soybeans with superheatedsteam evaporating from water processed by an oxygen removing treatmentand containing little or no oxygen for a predetermined time to obtainboiled bean juice containing soybean protein which is extracted from theboiled soybeans, the boiled bean juice including a solid matter of theboiled soybeans; p1 manufacturing soybean milk in which the soybeanprotein is suspended and which contains oxygen dissolved therein in anamount of 5 ppm or less by separating the solid matter from the thusobtained boiled bean juice without cooling it in an oxygen-freeenvironment; filling the soybean milk into a soybean curd manufacturinginsulated container or tearing open a soybean milk pack manufactured byfilling the soybean milk into a pack container without heating it andwithout cooling it and filling the soybean milk contained therein intothe soybean curd manufacturing insulated container; adding a suitableamount of a coagulant to the soybean milk in the soybean curdmanufacturing insulated container and sufficiently mixing the coagulantwith the soybean milk to obtain a mixed solution; immersingnon-corrosive electrodes in the mixed solution; passing an alternatingcurrent between the non-corrosive electrodes under such conditions thatno electrolysis occurs in the mixed solution; and manufacturing asoybean curd by coagulating the soybean protein by heating the mixedsolution from passing of the alternating current.
 7. The soybean curdmanufacturing method according to claim 6, characterized in that theground soybeans are boiled with the superheated steam to obtain boiledbean juice for manufacturing the soybean curd by the steps of: using acaldron comprising a caldron main body having a chart port disposed inthe vicinity of an end thereof and a discharge port disposed in thevicinity of the other end thereof with both the ends closed, at least asteam injection pipe installed in the caldron main body and having aplurality of steam injection ports disposed along the longitudinaldirection of the caldron main body and a steam generation means, whereinthe superheated steam is injected from the steam injection ports in atleast an inclined direction from radial direction of the steam injectionpipe so as to be supplied in at least a circumferential direction in thecaldron main body; charging the ground soybeans through the charge port;supplying the superheated steam generated by the steam generation meansto the steam injection pipe; injecting the superheated steam from theplurality of steam injection ports of the steam injection pipe andsupplying the superheated steam in at least a circumferential directionof the caldron main body; mixing the ground soybeans with thesuperheated steam to obtain a mixture and stirring the mixture whilefluidizing the ground soybeans and boiling the ground soybeans to obtainthe boiled bean juice containing soybean protein; and discharging theboiled bean juice through the discharge port.
 8. The soybean curdmanufacturing method according to claim 7, characterized in that thesuperheated steam injected from the plurality of steam injection portsof the steam injection pipe are supplied in a same circumferentialdirection in the caldron main body, or the superheated steam injectedfrom a portion of the plurality of steam injection ports and thesuperheated steam injected from the remaining portion thereof aresupplied in opposite circumferential directions in the caldron mainbody, respectively.
 9. The soybean curd manufacturing method accordingto claim 7, characterized in that the caldron further comprises acooling means disposed to the caldron main body on a discharge sidethereof for cooling the boiled bean juice and remaining steam of thesuperheated steam in the caldron main body.
 10. The soybean curdmanufacturing method according to claim 7, characterized in that thesteam generation means includes an oxygen removing means.
 11. Thesoybean curd manufacturing method according to claim 7, characterized inthat the superheated steam contains no oxygen.
 12. The soybean curdmanufacturing method according to claim 7, characterized in that thecoagulant is nigari.